Stimulation of prostaglandin synthesis by bradykinin and thrombin and their mechanisms of action on MC5-5 fibroblasts.

Transformed mouse fibroblasts, in which [3H]arachidonic acid was incorporated in the cellular lipids, released radioactive materials into the medium when stimulated by bradykinin and thrombin. Most of this released radioactivity was found in the landins; the remainder was present in the arachidonic acid fraction. When the cells stimulated by serum or when they were mechanically manipulated, not only prostaglandins but also high levels of arachidonic acid were released. Anti-inflammatory steroids, which decrease the availability of arachidonic acid, inhibited the stimulated release of prostaglandins caused by the vasoactive agents, suggesting that bradykinin and thrombin stimulated prostaglandin synthesis by increasing deacylation of the phospholipids. The efficiency of the conversion of the released arachidonic acid into prostaglandins appears to reflect the cellular proximity of the phospholipid deacylating activity and prostaglandin synthesizing system.